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THE COMPARATIVE VALUE OF FOODS FOR 
RAINBOW TROUT AND OTHER SALMONOIDS 

By Charles L. Paige 

Paper presented before the Fourth International Fishery Congress 
held at Washington, U. S. A., September 22 to 26, 1908 

BULLETIN OF THE BUREAU OF FISHERIES ;::::: VOL. XXVIII. P. 795-798 
Document No. 679 ::::::::::::::::::: : IbuoJ April. 1910 






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THE COMPARATIVE VALUE OF FOODS FOR RAINBOW TROUT 
AND OTHER SALMONOIDS. 



Bv CHARLE.S L. PAIGE. 



To demonstrate the comparative value of different kinds of food for voung 
salmonoids wi_th any degree of exactness must necessarily entail very patient 
and careful investigation. The fishes experimented with will have to be main- 
tained in separate pools, under identical provisions of environment, water supply 
and area, temperatures, and the possible supplies of natural food carried by 
or existing in the water or in the pools themselves. Where there exists wide 
diversity of opinion as to food values for the higher orders of animals, to demon- 
strate the values of such atomic particles as are collected by the young fish will 
tax the powers of the most exact scientific analyses. Any demonstration of the 
maintenance of the fishes will in itself be subject to question as to specific heredi- 
tary influences, climatic or aquatic conditions, prevailing habits of the fishes, 
and many other circumstances for consideration. 

After experiments and study covering a period of many years, supplemented 
by close observation of the fish in small areas of inclosed water, I can suggest no 
new form of food artificially prepared superior in any respect to that commonly 
used in most hatcheries where young salmonoids are fed. For fry I should prefer 
these foods in the order here named : 

1. Raw beef liver, finely ground, for the first five days or week. 

2. Fresh lean meat finely ground. 

3. Any available fresh lean meat mixed with increasing portions of wheat 
middlings, fed either in the raw state or after being cooked as a mush. 

In the preparation of any meat food (after five or six days feeding of raw 
fiver alone to newly hatched fry) the fresh liver and meat should be thoroughly 
ground together with from one-fourth to three-fourths of its weight of wheat 
middlings. The middlings, in itself good food which will sustain fish indefinitely, 
is particularly valuable in absorbing and holding the juices of meats and makes 
a mixture of about the right consistency and gravity to remain in suspense or 
slowly sink in water, while it is easily distinguished by the fishes once they are 

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accustomed to it. It is a cheap and generally available staple. Food prepared 
as described may be readily dried and preser\^ed for emergencies where a fresh 
supply of meat is lacking. 

That millions of trout and salmon fry have been and are being maintained 
in overcrowded hatching troughs upon a diet of beef liver would appear to 
be positive evidence of its great value, while it is commonly as easily and cheaply 
obtainable as any form of animal food. 

The chief object of this paper, however, is to suggest that young salmons 
and salmonoids reared in captivity should be given the minimum quantity of 
artificial food and a maximum area and flow of water containing their natural 
food, for which they should be permitted to forage. Prepared food should 
supplement the natural supply where water area is overcrowded with young fish, 
or where drouth, cold, or other climatic conditions interfere with the normal 
natural supply. In support of this view is offered the following summary of 
well-known or readily ascertained facts and examples: 

1 . That along the salmon rivers and trout streams fry existing under natural 
provisions are commonly in excellent physical condition, mortality among them 
being mainly caused by abnormal disturbances of the nests, such as fioods, 
drouths, or extraordinary climatic changes, or by the depredations of natural 
enemies, birds, reptiles, and other animals. 

2. That salmonoids are not surface-feeding fishes exclusively, but seek 
food suspended in the water and on the shores and bottom surfaces accessible 
to them; and that of necessity they must collect more or less vegetable and sedi- 
mentary matter; in fact, that they are rather omnivorous than piscivorous or 
carnivorous fishes. 

3. That under normal natural conditions a continuous succession of season- 
able aquatic and insectiverous foods, much of which will embrace vegetable 
matter in some form, is supplied to the young fish. 

4. That owing to the minute particles of food matter collected by newly 
hatched salmonoids, it is doubtless impossible to distinguish with accuracy the 
natural or instinctive selections made by them, or to determine nutritive values. 

5. That it will appear that suitable natural food for salmonoids is abundant 
in the waters wherever trout and salmon spawn, and that the most available, 
economical, and scientific provision for young salmonoids may be made in the 
preparation and adaptation of sufl[icient water area in normal natural condition, 
but subject to control as regards floods, drouths, freezing to extremes, and the 
exclusion of destructive animals. Controlled areas of stream or prepared runs 
should provide for the absolute regulation of the water flow, and should contain 
trap pools or other devices for collecting the fish, excluding them at the end of 
the spawning season, and finally reducing the flow of water to a minimum for 
the purpose of capturing the fry or young as may be desired. 



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